The following publications are believed to represent the current state of the art:
U.S. Pat. Nos. 6,400,871; 6,233,085; 5,896,219; 4,648,092; 6,882,781; 5,946,130; 6,580,534; 5,737,459; 6,717,719; 7,336,363; 4,860,279; 5,023,882; 7,088,743; 6,404,784; 6,144,677; 6,366,356; 6,678,294; 6,480,327; 4,757,268; 5,121,400; 4,761,059; 4,833,683; 4,979,804; 5,233,673; 6,200,309; 4,649,351; 5,661,747; 3,590,248; 7,239,777; 6,385,288; 4,794,345; 5,835,261; 5,539,571; 7,027,475; 7,187,492; 7,233,433; 7,058,098; 6,813,069 and 5,694,408;
U.S. Patent Publication 2006/0239312; and
“One Dimension Scaling of 100 Ridge Waveguide Amplifiers”, K. H. No et al, IEEE Photonics Technology Letters, Vol. 6, No. 9, pp 1062-66.